Removing Viruses From Drinking Water

University of Delaware's (UD) patented technology, incorporates highly reactive iron in the filtering process to deliver a chemical "knock-out punch" to a host of notorious pathogens, from E. coli to rotavirus.

"What is unique about our technology is its ability to remove viruses − the smallest of the pathogens − from water supplies," Pei Chiu, an associate professor in UD's Department of Civil and Environmental Engineering, said. Viruses are difficult to eliminate in drinking water using current methods because they are far smaller than bacteria, highly mobile, and resistant to chlorination, which is the dominant disinfection method used in the United States, according to the researchers. "By using elemental iron in the filtration process, we were able to remove viral agents from drinking water at very high efficiencies. Of a quarter of a million particles going in, only a few were going out," Chiu noted.

The elemental or "zero-valent" iron (Fe) used in the technology is widely available as a byproduct of iron and steel production, and it is inexpensive, currently costing less than 40 cents a pound (~$750/ton). Viruses are either chemically inactivated by or irreversibly adsorbed to the iron, according to the scientists. The technology is effective against human pathogens including E. coli 0157:H7, hepatitis A, norovirus and rotavirus.

"In 20 minutes, we found 99.99 percent removal of the viruses," Chiu said. "And we found that removal of the viruses got even better than that with time, to more than 99.999 percent." The elemental iron also removed organic material, such as humic acid, that naturally occurs in groundwater and other sources of drinking water. During the disinfection process, this natural organic material can react with chlorine to produce a variety of toxic chemicals called disinfection byproducts.